PLANT INDUSTRIES 315 



animal enemies that the plant may encounter in its new grow- 

 ing place. Thus when corn, which naturally thrives best as 

 a tropical or sub-tropical plant, is grown in the north central 

 states, the shortness of the season may not allow time for 

 ripening the ear ; but by experimentation certain varieties of 

 corn have been discovered or developed (see chapter on Plant 

 Breeding) in which the plant is not so large as the average, 

 and the ear, though somewhat smaller, matures in less time. 

 Some kinds of seed corn are advertised by the salesmen as 

 " ninety -day corn," which means that the plant will grow and 

 ripen a new ear within ninety days, while in case of some 

 other varieties of corn more than double that time is required 

 for it to mature. Furthermore, in the case of wheat some 

 varieties are much less readily affected by the rust diseases 

 than are other varieties ; some thrive best in certain regions 

 when planted in the late autumn (winter wheat) ; and others 

 in other regions thrive best when planted in early spring 

 (spring wheat). Every civilized or even partially civilized 

 nation depends largely upon one or more of the cereals, and 

 in spite of the fact that the nations have been dependent upon 

 them for so long, the practices relative to selection of seed, 

 cultivation, prevention of diseases, and utilization of the prod- 

 ucts have changed very little from decade to decade. The 

 application of scientific principles to the production of cereals 

 has already shown great possibilities of improvement in plant 

 production, but only the most intelligent agriculturists utilize 

 these investigations, the traditional " practices of the fathers " 

 often dominating the majority of those who till the soil. No 

 doubt the decades immediately to follow will bring much new 

 scientific knowledge about the growth of cereal crops, and 

 nothing seems more fundamental than the application of those 

 sciences which may lead to a more effective production of the 

 world's food supply. 



298. Horticulture. Fruits and berries have constituted a 

 considerable part of the food of men throughout the period 

 covered by history. Wild apples, grapes, and berries, in nearly 



